=over

=item ${^WARNING_BITS}
X<${^WARNING_BITS}>

The current set of warning checks enabled by the C<use warnings> pragma.
It has the same scoping as the C<$^H> and C<%^H> variables.  The exact
values are considered internal to the L<warnings> pragma and may change
between versions of Perl.

This variable was added in Perl v5.6.0.

=back